1. Technical Field
The present disclosure relates to an optical lens system, an image capturing unit and an electronic device, more particularly to an optical lens system and an image capturing unit applicable to an electronic device.
2. Description of Related Art
In recent years, with the popularity of electronic devices having camera functionalities, the demand of miniaturized optical systems has been increasing. The sensor of a conventional optical system is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical systems featuring better image quality.
A conventional optical system employed in a portable electronic product mainly adopts a third-element lens structure. Due to the popularity of mobile terminals with high-end specifications, such as smart phones, tablet personal computers, wearable apparatus and driving assist devices, the requirements for high resolution and image quality of present compact optical systems increase significantly. However, the conventional optical systems cannot satisfy these requirements of the compact optical systems.
Other conventional compact optical systems with four-element lens structure are developed to enhance resolution and image quality. However, since the second lens element is too thin to be manufactured, the optical system is easy to become fragile, which lacks stability for the optical lens system. Therefore, the functionality of telephoto is worse, which is not favorable for capturing an imaging object far away from the optical system. Moreover, the optical system with insufficient telephoto performance excessively enlarges a chief ray angle of the optical system, which causes the reduction of a relative illumination of the optical system, thereby resulting in vignetting at the peripheral region of the image.